The I in science
It seems to be hard-wired into the brains of many students, that scientific writing by definition goes without the first person, and preferably even in the passive voice. To say "the daily interactions in the laboratory under study were observed closely roughly at weekly intervals for a period of several months", rather than "we attended laboratory activities every week for a few months, and made detailed reports of what we saw". The first is then thought to be more objective and neutral than the first. But, as a starter, can you explain how the first actually offers 'better' knowledge, and if so to which criterion, than the second? - No, neither can I.
Of course, it is not too difficult to see where the idea comes from. Science in general aims at producing knowledge in such a way that this knowledge is closest as possible to the truth. Science does indeed not produce conclusive truths, since scientists do not have any special access to knowledge of any sort. What science does have at its disposal, though, is that it has over centuries produced a repertoire of methods that help driving out certain mistakes. (And this is one of the reasons why science is not 'just another opinion', should this thought occur to you after reading that science does not produce truth.)
In this pursuit of the best possible truth, it seems indeed tempting to drive out the scientist: the unruly and fallible individual who in fact is rather a disturbance to neutral observations than anything good. This is what driving out the "I" from science tries to accomplish.
But think about it. One of the many principles developed by scientific practice to drive out mistakes is transparency. It comes in many forms, one being the idea that it should be somehow visible for the receiver of knowledge to know how that knowledge came about. No matter how beautiful or welcome a particular piece of knowledge is, a good scientist will only accept it if the knowledge is acquired in a sufficiently thorough, systematic, and above all critical way. And exactly part of this transparency is in fact eliminated if you hide the "I" from the story. So in some way, talking in passive forms makes the writing less scientific.
But there is even more to say. Social studies of scientific practice have taught us many lessons, one being that the actual shape of scientific knowledge, or of technologies for that matter, can only be understood if we take into account the situation in which they were made - including the people who were involved in the making. Now, when you dissect a frog on the lab bench, it may not matter that much - indeed - who does the actual cutting (though maybe it does). But in the case of studying social practices in laboratories, it really matters who does the visiting and observing. Interactions will likely be different if a grey-haired female professor enters the lab to observe, than when a fresh male PhD does. People will react differently and respond differently in either case. (Yes, this is sexist. And that is so because the research material, the laboratory and its microsocial mechanisms, is likely to contain sexist structures, even if it has a proper gender-neutrality policy in place.) Especially in social sciences and humanities, the "I", or more generally a first-person perspective, is much more accepted and even needed. Social scientists and humanities scholars are a special breed in the sense that they, at times, interact with their very research material.
Does this mean that you should use the first person in about every sentence? No, not quite. While it is good to avoid the passive voice - it is also, on a side note, ugly, as it produces a disengaging and cold atmosphere, rather than drawing the reader in - you should not bring in the first person inadvertently either. It should come in naturally for the reasons given above. Because it was you who interacted with the population under study. Or because it is you who makes a contribution to a debate: you better make sure you 'own' what you say, and be willing to defend it. No one else is going to stand up for you, and certainly a passive voice is not.
And, on a concluding note: don't use "I" in a way that kills your assertivity. Don't say: "I will try to show that ...", but: "I argue that ...". Being transparent and reflexive about the fact that it is you doing the research is not the same as saying it is probably no good. Or so I hope.